I. Field of the Invention
This invention relates generally to the design of an improved delivery system for applying adhesives. More particularly, the delivery system includes a novel sprayer assembly for combining adhesives which are stored separately as fluids then applied to a surface as a spray or stream. Although useful for any adhesive made from at least one solution, the delivery system is useful for combining tissue adhesive components such as a first solution of fibrinogen and a second solution of thrombin. Upon contact with one another, these two solutions undergo a rapid chemical reaction which causes curing into a functional tissue adhesive. Thus, it is desired to keep these two solutions separately confined until just prior to the time of direct application on a patient and then thoroughly and rapidly mix them for treatment of a wound.
II. Description of the Prior Art
The treatment of wounds on patients typically involves suturing or covering the wound with an external dressing. There are some applications, however, where the external dressing or sutures are not effective or even act as an irritant. In situations such as treatment of internal body cavities, it has been discovered that treatment of the wound with the body's own healing compounds has been very effective in inducing wound closure and subsequent healing. A common treatment takes advantage of the rapid reaction which occurs when a solution of clotting factors, such as fibrinogen, comes into contact with a solution of a catalyst, such as thrombin, to form a complex which acts as a tissue adhesive. This rapid reaction typically commences within 2 seconds after the solutions initially contact one another, and it typically attains a soft set within 10 seconds of contact. A common name for such a complex is fibrin glue.
Prior fibrin glue delivery systems may generally be categorized as utilizing either turbulence within a solution or overlapping contact of airborne sprays to obtain mixing. The apparatus utilized by either of these systems typically includes confining a fibrinogen solution separately from a thrombin solution, then permitting these two solutions to mix either immediately prior to or upon application on a wound. Typically, these solutions are confined within separate syringes prior to mixing.
An example of a delivery system based on the mixing of overlapping jets of airborne particles is provided in U.S. Pat. No. 4,874,368, which was issued on Oct. 17, 1989 to Miller, et al. This device provides an easily manipulated dual syringe apparatus which enables the two solutions to stream from a sprayer and mix upon application over a wound. A connecting clip member is fitted on each of the piston-type plungers inserted into each syringe. The tip of each syringe is fitted with a specially formed needle, bent to receive the initially parallel outflow from each syringe. The bend in each needle redirects the outflow through a hollow plastic sleeve which serves as a retainer for the long, parallel needle tips. These tips extend slightly beyond the distal end of the hollow sleeve. As solution exits each tip, it is propelled into a spray or stream. The trajectories of the sprays partially overlap and begin mixing either while airborne or as they strike the surface being treated. The clotting reaction commences as the solutions contact one another, due to the close positioning of the needle tips, and spray from one tip can come to rest at the orifice of the other. While temporarily not being used as the surgeon is preoccupied with other matters, contaminants from one tip can cause the clotting reaction to propagate retrograde into the confines of the other needle, plugging the system against further use. Also, thoroughness of mixing depends somewhat upon the technique used by the surgeon.
Syringe applicators employing a mixing chamber are directed toward minimizing the contact time of such solutions prior to application. An example of such a system is provided by U.S. Pat. No. 4,978,336, issued on Dec. 18, 1990 to Capozzi, et al. This biological syringe system includes first and second syringes containing individual components of a tissue adhesive. A manifold locks onto the two syringes and receives the output stream from each syringe. Alternatively, these output streams may be delivered to either a conventional needle or an output nose which terminates in a spray outlet. Mixing of the solutions either occurs within the lumen of the needle or within a mixing space provided within the output nose. In either embodiment, the combination is atomized as it is ejected from the device, either at the tip of the needle or by a spray outlet on the output nose, for atomized application to a wound. This device is similar to other available mixing chamber-type devices because the two solutions are introduced into the mixing chamber from initially parallel ports. Thus, the degree of turbulent flow attained is somewhat dependent upon the Reynolds numbers for the solutions, which contribute to the vortices or eddies which are produced within the chamber. It is also affected by the rate at which the solutions are introduced into the chamber. Furthermore, if the syringe plungers are depressed at a very slow rate, the reacting mixture is not evacuated from the system quickly enough and clotting can occur within the output nose or within the mixing chamber. Thus, it has been found that for quickly reacting substances, such as fibrin glue components, it is desired to have a rapid but uniform mixing that is less dependent on the rate at which the user introduces the solutions into the mixing chamber than that attained in the Capozzi, et al. device.
A syringe-type device for applying a tissue adhesive which seeks more thorough mixing of solutions is disclosed in U.S. Pat. No. 4,735,616, issued on Apr. 5, 1988 to Eibl, et al. This device includes parallel syringes mounted within a holding means. The distal tips of the syringes are attached to a connecting head having connecting channels directed at an angle toward a mixing needle. Thus, each solution enters the mixing needle in a stream which is deflected off the side of the needle to enhance mixing. This device lacks a separate chamber in which this mixing can occur and relies upon mixing as the fluid moves along the connecting channel of the needle applicator. The solutions mix due to predictable, Bernoulli-type turbulent eddies created along the walls of the mixing needle. The length of the mixing needle which receives each of the solutions is calculated to permit them to adequately mix upon contact with one another. Since the clotting reaction occurs so quickly, the length of the mixing needle is no longer than necessary to provide adequate mixing. It has also been found with this device that there is a minimum rate at which the plungers must be depressed into the syringes, below which duration of contact within the mixing needle is excessive and permits clotting therein. Thus, it is once again desirable to have a reliable mode of mixing of the solutions which will both permit a minimum duration of contact prior to application to a wound and not be as dependent upon external factors such as the rate of depression of the syringe. Consequently, it is desirable to eliminate any requirement for spraying a premixed solution.
An additional fault which is characteristic of any system in which mixing occurs within the device is that this rapid reaction, once catalyzed, can propagate retrograde through the entire system and into the syringe containing the solution of clotting factors. Thus, forward flow through the device must exceed the rate at which the reaction can propagate in a retrograde manner. Unless the user has been made aware that this can occur, he may be unaware of the minimum rate at which he should depress the syringes to counteract this tendency.
It is accordingly a principle object of the present invention to provide a new and improved physiologic glue delivery system which permits rapid and complete blending of two solutions.
Another object of the present invention is to provide a new and improved method and apparatus for mixing and applying physiologic glue which eliminates the need for mixing within the device, so the clotting reaction cannot plug an exit nozzle or needle and cannot propagate retrograde into either solution syringe.
It is yet another object of the present invention to provide a new and improved method and apparatus for mixing and applying physiologic glue prior to the time that the mixed solutions begin to cure and attain a soft set state.
A further object of the present invention is to provide a new and improved method and apparatus for mixing and applying physiologic glue using a variety of solution reservoirs, including syringe reservoirs, which are either equally or differently sized.